The unit hertz (Hz) is a measure of frequency, with 1 hertz indicating that whatever you're measuring occurs once per second; for example, if your computer screen refreshes itself 40 times per second, the refresh rate would be 40 hertz. Horsepower (HP) is a unit of power, the amount of work performed over a period of time. Since these two units don't measure the same thing, they can't be directly converted. However, if you have a certain amount of work occurring at a certain frequency, you can state that in terms of horsepower.
Mechanical horsepower is used in the United States and England, but in the rest of Europe, a slightly different unit of measurement called metric horsepower is used. To convert to metric, divide your power in mechanical horsepower by the conversion rate: 1 mechanical HP = 1.01387 metric HP
There are other types of horsepower for different situations, including boiler horsepower and electric horsepower (see References for more information).
Check that you have a measure of work and a measure of frequency. Work is often measured in foot-pounds (ft-lbs, standard), Joules (J, metric) or Newton-meters (N-m, equivalent to a Joule); frequency is measured in hertz. If your work is measured in foot-pounds, skip to Step 3.
Convert your work in Joules (or the equivalent Newton-meter) to foot-pounds. Divide the amount of work in Joules by the conversion rate: 1 J = 0.737562149 ft-lbs.
Convert your work and frequency to power. To do this, take your work (in foot-pounds) and the frequency at which that work occurs (in hertz) and simply multiply the two values together.
You now have a unit of power called foot-pounds per second (ft-lbs/s). To convert this unit to mechanical horsepower, divide it by the conversion rate: 1 HP = 550 ft-lbs/s
About the Author
Matt Edmonds began his writing career in 2011. He specializes in cognitive science, specifically language development in children, as well as the performing arts. Edmonds graduated from Northwestern University with a Bachelor of Arts in communications.
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